The ability to prepare and control the quantum state of a quantum system is important for quantum information processing. Just as a classical computer memory should have the ability to initialize bits and implement gates to change the state of a bit from zero to one and vice versa, a quantum computer should be able to initialize the state of the quantum system used to store quantum information and the quantum system should be able to be controlled to implement logical gates that change the quantum state of the quantum system.
Quantum information may be stored in any of a variety of quantum mechanical systems. Conventionally, quantum information may be stored using quantum bits, referred to as “qubits,” which are typically two-state quantum mechanical systems. However, many-state quantum systems, such as quantum mechanical oscillators, may also be used to store quantum information.